It was a quite a bang. In fact, it was the biggest one in the universe since the Big Bang itself, say astronomers in a news release. Using data from multiple telescopes—including NASA's Chandra X-Ray Observatory—astronomers reported Thursday that the long-ago blast came from a black hole in a cluster of galaxies 390 million light-years away, per the AP. The explosion was so large it carved out a crater in the hot gas that could hold 15 Milky Ways, says lead author Simona Giacintucci of the Naval Research Laboratory in Washington. Astronomers believe the explosion came from the heart of the Ophiuchus cluster of thousands of galaxies: a large galaxy at the center contains a colossal black hole.
"We've seen outbursts in the centers of galaxies before but this one is really, really massive," says Melanie Johnston-Hollitt of the International Centre for Radio Astronomy Research. "And we don't know why it's so big. But it happened very slowly—like an explosion in slow motion that took place over hundreds of millions of years." The blast is believed to be over by now: There are no signs of jets currently shooting from the black hole. The first hint of this giant explosion actually came in 2016 when Chandra images of the Ophiuchus galaxy cluster revealed an unusual curved edge. More observations are needed in other wavelengths to better understand what occurred, say the team. The findings appeared in the Astrophysical Journal. (Read more space exploration stories.)